Devices for stacking generally planar articles of material, such as sheets of corrugated material, are well known. One example of a commercially available device is the AGS2000 Rotary Die Cut Stacker made by the assignee of the present invention, A.G. Machine, Inc., Weyers Cave, Va. Further examples of such devices are disclosed in U.S. Pat. No. 3,321,202 to Geo. M. Martin and U.S. Pat. No. 3,419,266 to Geo. M. Martin, each of which is expressly incorporated herein by reference in its entirety.
FIGS. 1-3 illustrate a conventional apparatus for stacking sheets. The stacking apparatus 100 generally comprises a layboy section 102 which receives sheets, such as corrugated blanks produced by a rotary die cut machine 103, and discharges the sheets onto a transfer conveyor 104. The transfer conveyor 104 receives the sheets and transports them to a main conveyor 106. The main conveyor 106 has an intake end 108 and a discharge end 110, and the transfer conveyor has an intake end 112 and a discharge end 114. At the main conveyor intake end 108, the main conveyor 106 is mounted to a base 116 at a pivot point 118 so that the main conveyor 106 may be pivoted to raise its discharge end 110. At the discharge end 110 of the main conveyor 106, an accumulator section 120 receives discharged sheets.
In operation, the main conveyor 106 is pivoted about the pivot point 118 to lower the discharge end 110 of the main conveyor 106 to an initial or lowered position, illustrated in FIG. 2. Sheets are fed onto the main conveyor 106 at its intake end 108, transported along the conveyor to its discharge end 110, and discharged from the conveyor toward a backstop 122 in the accumulator section 120. The sheets settle down, typically onto a discharge conveyor 132, to form a stack of sheets.
As additional sheets drop onto the stack, the main conveyor 106 is pivoted to raise the discharge end 110 thereof vertically so that the sheets are discharged above the top of the growing stack. If the pivot point 118 were laterally fixed, the discharge end 110 of main conveyor 106 would follow an arc about pivot point 118 and move laterally away from the stack as the discharge end 108 of the main conveyor 106 was raised. This would likely interfere with the efficient formation of a stack of sheets. Therefore, the intake end 108 of the main conveyor 106 is supported by pivot arm 126 which pivots relative to base 116 and the main conveyor 106. This allows the discharge end 110 of the main conveyor 106 to move generally vertically instead of following an arc and causes the intake end 108 of the main conveyor 106 to move laterally toward the stack as the discharge end 110 of main conveyor 106 rises.
While this movement of the intake end 108 of the main conveyor 106 helps ensure proper stack formation, it also pulls the transfer conveyor 104 away from the layboy section 102 and creates a gap between intake end 112 of the transfer conveyor 104 and the layboy section 102. This problem has previously been addressed by providing slats 128 (illustrated in FIG. 3) extending from the discharge end of the layboy section 102 toward transfer conveyor 104. As the intake end 108 of the main conveyor 106 moves away from the layboy section 102, it moves the transfer conveyor 104 away from the layboy section 102 as well. However, the slats 128 span the gap between the layboy 102 and the transfer conveyor and prevent a gap from opening up as the transfer conveyor moves. This, in turn, helps ensure that product exiting the layboy section 102 will reach transfer conveyor 104.
The slats 128 partially address the problem discussed above. However, they are relatively narrow, and small products and/or scrap material still occasionally catches on the slats.
Another method for addressing this problem is shown and described in U.S. Pat. No. 7,753,357 assigned to the assignee of the present application, which is incorporated herein by reference. The '357 patent describes a transfer conveyor that has a first end connected to the main conveyor and a second end connected to the layboy section. A belt tensioning system is provided that allows the length of the transfer conveyor to change so that a gap is not created between the layboy section and the transfer conveyor when the main conveyor deck is raised.
This approach works well in certain environments. However, it is sometimes necessary or desirable to use a transfer conveyor (transfer deck or diverting conveyor) that must be fixed in the length (sheet transport) direction. In such cases, when the discharge end of the main conveyor rises, the intake end of the main conveyor pulls away from the stationary diverter/transfer deck and leaves a gap into which sheets of material may fall.